Ozone generator



Nov. 30, 1965 c. H. FULLER 3,220,943

OZONE GENERATOR Filed Jan. 16, 1963 2 Sheets-Sheet 1 INVENTOR. CHARLES IMEVEY FULLE'E C- H. FULLER OZ ONE GENERA TOR Nov. 30, 1965 2 Sheets-Sheet 2 Filed Jan. 16, 1965 I NVENTOR.

United States Patent Office 3,220,943 Patented Nov. 30, l9ii5 3,220,?43 ()ZONE GENERATOR Charles Harvey Fuller, Los Angeles, Calif. Filed Jan. 16, 1963, Ser. No. 272,171 6 Claims. (Cl. 204-315) This application is a continuation-in-part of my application, Serial No. 14,761, filed March 14, 1960, under the same title, now abandoned.

This invention has to do with ozone generators of the type in which an electrical discharge takes place in the atmosphere between parallel closely spaced gaseous discharge tubes. Alternating current power is supplied at several thousand volts to electrodes provided in opposite ends of adjacent tubes. Current is transmitted along each tube by ionization of the contained gas, producing low power discharge between adjacent tubes by capacitive action across the tube walls.

A primary purpose of the present invention is to provide an ozone generator of the described type which is capable of operating under extreme conditions of humidity and temperature variation such as tend to short-circuit electrical equipment of conventional construction.

An illustrative example of such operating conditions is to be found in commercial cold storage lockers. Ozone generators are known to be of value in such lockers for preserving meat and produce against mold, but have not previously been capable of satisfactory operation under such unfavorable conditions. The improved structure of the invention permits reliable operation not only in humid atmospheres, but even in the presence of corrosive and electrically conductive impurities in the atmosphere, such as salt, for example, which are typically present in meat storage rooms.

A further feature of the invention provides an ozone generator of greater capacity per unit of size or weight than has previously been available. That is accomplished by employing a high pressure of ionizable gas within the individual discharge tubes. I have discovered that such high pressure permits the use of small diameter tubes while maintaining excellent uniformity of atmospheric discharge longitudinally of the tubes.

Whereas an increase of gas pressure in the discharge might be expected to increase the electrical resistance and thereby reduce the current and power available in the discharge, especially in small tubing, I have discovered, on the contrary, that provision of gas pressures radically higher than those previously employed lead to higher currents in the discharge. That increase occurs when comparisons are made at moderate voltage; and is particularly marked as the supply voltage is increased. Thus, for example, I have found that at conventional gas pressure an increase of voltage from 5,000 to 8,000 volts, say, produces only negligible increase in current and in ozone production; but at the radically increased gas pressure of the present invention, the same voltage change. typically substantially doubles the ozone produced.

That remarkable increase in ozone production accompanies a distinct change in the nature of the gas discharge. At conventional gas pressures, typically from 6 to 8 mm. of mercury, as in normal neon sign practice, the discharge in each tube of an ozone generator array is confined primarily to the central portion of the tube. The discharge displays side arms of rounded form and indefinite boundaries which extend from the central discharge irregularly and intermittently toward the tube Wall in the plane of the array. Those projections of the discharge occur at rather widely spaced intervals longitudinally of the tube. The relatively low ozone production obtainable with conventional gas pressures seems to be associated with the intermittent and widely spaced nature of those deviations of the discharge and the relatively low current that they carry.

When the gas pressure is doubled or quadrupled in accordance with the present invention, the activity within the tubes is radically different. The discharge can be seen to substantially fill the tube in the plane of the tube array, maintaining strong though irregular activity closely adjacent the tube wall. That activity adjacent the wall comprises small sharply defined and closely spaced discharge centers that occupy substantially the entire tube length, in contrast to the relatively widely spaced, isolated and vaguely defined areas of mild energization in previous practice. And the bright discharge centers adjacent the wall vary rapidly in time, so that power is made available substantially continuously to all sections of the tube. As a result, substantially the entire length of each tube is accessible for ozone-producing discharge at every alternation of the voltage. Morevover, that new quality of gas discharge is more marked and more effective for ozone production when tubes of small diameter are used.

The invention further provides a particularly convenient and economical mounting structure for the discharge tubes that is completely foolproof and safe in operation.

A particularly important further object of the invention is the provision of mounting structure for the 'discharge tubes which permits the spacing between adjacent discharge tubes to be modified conveniently and without disassembling them. That permits the ozone generator to be used with maximum effectiveness and convenience either in a normally dry atmosphere, where a relatively small tube spacing is required, or in an excessively humid atmosphere such as has been described, where a greater tube spacing is required.

The provision of convenient and accurate means for adjusting the spacing between tubes further permits minor variations among the tubes to be compensated by individual adjustment. I have discovered that the strength and uniforimty of the discharge often varies in a critical manner as the inter-tube spacing is changed, and can readily be observed visually. With the structures of the invention it is possible to make final adjustment of the tube spacing while the discharge is operating. The various spacings can then be set to give optimum strength and uniformity of discharge in each tube. In that way individual diiferences among the tubes are compensated.

More particularly, the described spacing adjustment permits optimum operation of the ozone generator to be maintained as the tubes age. I have discovered that when the discharge in an individual tube of the array becomes weakend, for example due to contamination of the conductive gas by release of any entrapped impurities, substantially normal operation can often be re-established by slightly reducing the spacing between that tube and its neighbors. The expense and inconvenience of tube replacement is thereby greatly reduced.

A full understanding of the invention, and of its further objects and advantages, will be had from the follow ing description of an illustrative embodiment. In that description, and in the accompanying drawings which from a part of it, the particulars of the described struc ture are intended only as illustration of the invention, and not as a limitation upon its scope, which is defined in the appended claims.

In the figures:

FIG. 1 is an elevation of an illustrative embodiment of the invention;

FIG. 2 is a plan; L

FIG. 3 is a fragmentary section on the line 33 of FIG. 1, at enlarged scale. a

FIG. 4 is a section on the line 44 of FIG. 3;

FIG. 5 is a section on the line 55 of FIG. 4;

assesses FIG. 6 is a section on the line 66 of FIG. 1;

FIG. 7 is a fragmentary elevation representing a modified structure for mounting the tubes of an array;

FIG. 8 is a plan corresponding to FIG. 7;

FIG. 9 is a detail at enlarged scale and partly in section showing an illustrative bracket structure in the aspect of FIG. 8;

FIG. 10 is an end view corresponding to FIG. 9; and

FIG. 11 is a section on line 1111 of FIG. 9.

My ozone generator, as illustratively shown in the drawings, comprises a supporting frame and housing, indicated generally by a numeral 10, a plurality of discharge tubes 72, arranged in a fiat array '70, and a power supply shown as a transformer 100 mounted within a chamber 109 of housing 10. Mounting studs may be provided as indicated at 11. The apparatus may be operated in any desired orientation with respect to gravity. For clarity of description and without implying any limitation, the orientation will be taken as that shown in FIG. 1, considered as an elevation.

Frame 10 comprises two parallel frame arms 12, the lower ends of which are joined by the frame yoke 14. Arms 12 and yoke 14 are of hollow construction, and may be typicallyformed of sheet metal. Yoke 14 comprises a channel member 15 which extends the entire width of the frame, and a cover member 16, which is also of channel form and covers the intermediate portion of channel 15 between the two frame arms. The channel flanges of members 15 and 16 overlap, as shown best in FIG. 6, and are releasably secured together as by the screws 17.

Frame arms 12 comprise the post members 20, which are fixedly mounted on the inner face of one of the flanges of yoke channel 15 at its opposite ends, as shown best in FIGS. 3 and 4; and the arm cover members 22, which are removably secured to post members 20, by the screws 23. The post and cover members together form vertical housing chambers 24, of rectangular section, which are fully enclosed except for vertical slots 26 in the opposing faces of the frame arms. Slots 26 are formed by the spacedly opposed edges 27 and 28 of the post and cover members and 22, respectively. Slots 26 are parallel and define the vertical plane indicated at 30 in FIGS. 3 and 4. Chambers 24 are closed at their upper ends by cover pieces 29, which are fixedly mounted on posts 20 and may be formed integrally therewith. A reinforcing member32 is preferably mounted between the upper ends of frame arms 12 to add rigidity to the frame structure.

Discharge tubes 72 extend horizontally between frame arms 12, with their opposite end portions extending through the slots 26 in the respective arms into chambers 24. The tubes are closely spaced in mutually parallel relation and form a fiat array 70 parallel to plane 30 and substantially coinciding therewith.

The tube ends are anchored in an effectively fixed, yet slightly yielding, manner within chambers 24 by means now to be described. Two parallel opposing cushion structures 43 and 44 are mounted within each chamber 24, extending longitudinally thereof in alignment with the slot 26 and closely adjacent thereto on opposite sides of plane 30. Each cushion structure comprises an elongated resilient pad member 45 and means for supporting the pad member and maintaining its longitudinal form substantially invariant. In the present embodiment that form is rectilinear. Each pad member is of generally triangular section and is supported by means of a rectilinear bracket 48 of channel form which embraces one side face of the pad, as shown best in FIG. 3. The opposite corner edge 49 of the pad is thereby exposed and is adapted to yieldably engage the discharge tubes.

One cushion structure 43 is fixedly mounted against the inner face of post member 20 by means of two bolts 50, placed near its upper and lower ends. The second cushion structure 44 in each chamber 24 is movably mounted by suitable means which permit its forcible and controlled movement toward fixed cushion structure 43. As illustrated, that adjusting means comprises the same bolts 50 and the nuts 52 (FIG. 4), which may be tightened to move the two channnel brackets and their carried pads toward each other. Means are also provided to positively limit that movement at a predetermined position appropriate to the selected diameter of discharge tubes 70. Such stop means are illustratively shown as the spacing sleeves 55, which engage opposing faces of channel brackets 48. The defined spacing between the two cushion structures is so selected that the exposed working faces 49 of pads 46 are appreciably resiliently compressed by each of the engaged discharge tubes, as shown best in FIG. 4. The tubes are thereby held firmly against accidental displacement, but may be manually movable in the plane of the tube array against the friction of the pads, as for fine adjustment of the spacing. Once the mutual spacing of adjacent tubes is correctly established, it typically remains effectively constant until tube aging necessitates readjustment, or until the apparatus is disassembled, as for replacement of a tube, for example.

During assembly of the described tube supporting structure, it is convenient to mount the fixed cushion structures 43 on post members 20, as illustrated, and then position frame 10 in a suitable jig with plane 30 horizontal. The discharge tubes are then inserted in slots 26 with their end portions resting on the installed cushion structures in approximately the desired position. Spacing members of sheets material of suitable thickness are inserted between adjacent tubes to define their mutual spacing. Spacing sleeves 55 and cushion structures 44 are then assembled, and the nuts 52 are applied and tightened, forcing the two opposed cushion structures together as far as spacers 55 allow.

The tubes are thereby all individually gripped simultaneously in a manner that is sufficiently yielding to avoid damage, but that defines the tube spacing accurately and effectively positively even after removal of the spacing sheets. Pads 46 may be made of any suitable resilient material. A satisfactory material is the synthetic rubberlike product known as neoprene and specially purified to make it resistant to presence of ozone inthe atmosphere. The dimensions of the pads and of the associated structures are so selected that discharge tubes 70 are positioned substantially in mid-plane 30 of housing slots 26. The tube spacing from slot edges 27 and 28 is typically from about /8 to about inch.

The preferred spacing between adjacent tubes, and hence the thickness of the spacing elements that are inserted between the tubes during assembly, depends not only upon the energizing voltage in the usual way, but also upon the use for which the ozone generator is intended. If the device is to be used under the extreme cond1tions of humidity that have been described a larger than normal spacing is required, in order to prevent effective shorting of the atmospheric discharge by drops of moisture that accumulate on the tubes. A spacing of as much as twice the value needed for normal atmospheric condition-s may be desirable for that purpose. An important advantage of the present tube supporting structure is that any desired tube spacing may be obtained without modification of the actual structure of the device. It is therefore possible, for example, to change the tube spacing of an existing device to conform to any desired environment in which it is to be used. For that purpose, it is only necessary to remove cover members 22 and release nuts 52. The tubes may then be respaced as desired, and clamped in their new positions by again tightening nuts 52. If the spacers 55 are of suitable length, the pressure of the pads upon the tubes may be made sufiicient to hold the tubes firmly under normal conditions, while permitting adjustment of the tube positions even without loosening the nuts.

Each tube 70 is provided with an electrode 74 at one end, and the tubes are arranged with the electrodes of adjacent tubes at opposite ends of the array. The electrodes may be of conventional construction, and are provided with flexible electrical leads 75 in the usual manner. All of the electrodes within each frame chamber 24, that is, the electrodes of alternate tubes of the array, are electrically connected together in parallel.

In accordance with one feature of the present invention, that connection is made by means of an electrically conductive bus member that is supported within chamber 24 in relatively widely spaced relation to the chamber walls. That bus member is shown illustratively at 76, and is typically provided with screws 77 for convenient connection of the leads 75. Bus members 76 extend generally parallel to the row of tube ends within each chamber, but are considerably shorter than the height of tube array 72. Each bus member 76 is fixedly mounted by a bracket structure of insulative material which provides a leakage path of at least several inches between the bus and the conductive housing structure on which it is mounted. As illustrated, that bracket structure comprises the elongated insulator 80 of generally U-form, the ends of which are fixedly mounted by means of the metal brackets 82 and 84 near the upper and lower ends of chamber 24, respectively.

Brackets 82 and 84 are typically 3-sided angle brackets, of which one side 83 is mounted within the pad-carrying channel 48 of cushion structure 43 by means of bolt 50, already described. Another side 85 of those brackets extends horizontally and carries the insulator 80. The third side 86 of each bracket lies in a vertical plane perpendicular to plane 30 and serves to block the end portions of slot 26 above and below the array of discharge tubes. As shown best in FIG. 5, the described structure provides insulative supports for bus 76 that are several inches long and that are well spaced over substantially the whole of that length from the walls of chamber 24.

I have found that for effective operation under the described unfavorable conditions it is essential to paint the entire surfaces of the electrical assemblies just described with an insulative and water impervious material, such, for example, as a high resistance insulative epoxy varnish. That coating is applied not only over bus member 76 and its insulative support 80, but also over the entire surface of bracket faces 86, the ends of power leads 102 and electrode leads 75.

Power for energizing tubes 70 and the atmospheric discharge between them is typically provided by a power transformer, indicated at 100. Alternating input power for transformer 100 is provided at conventional voltage via input leads indicated at 101. Power from the transformer secondary Winding at elevated voltage is supplied via the two high tension leads 102 to the respective bus members 76. Leads 102 are insulated with heavy duty insulation capable of withstanding the elevated voltage, which is typically from about 5,000 to about 10,000 volts.

In accordance with the illustrated structure, transformer 100 is fixedly mounted on an external face of frame housing 12, shown as the lower face of frame yoke 14. The transformer is enclosed by housing structure forming the transformer chamber 109. High tension leads 102 are led from chamber 109 into the interior of frame yoke 14, as through the grommetted aperture 110. The hollow interior of yoke 14 communicates at its opposite ends with chambers 24 in the two frame arms 12, permitting convenient access for leads 102 to the respective bus members 76 without at any point extending outside of the protective housing structure.

In the modified tube mounting structure represented illustratively in FIGS. 7 to 11, a rigid supporting frame is formed of the heavy channel members 122 and 123, which are typically vertical, and the lighter transverse channel members 124 and 125. That frame may be supported in any desired manner, either within the main chamber to be treated with ozone, or within a small chamber through which air is blown to carry ozone to the main treatment room. Transverse members 124 and 125 carry a system of parallel spaced tracks, shown illustratively as four in number and of channel section. In the present embodiment, tracks 126 and 127 carry the alternate tubes 72a that have their electrodes at the right end as seen in FIGS. 7 and 8; and tracks 128 and 129 carry the alternate tubes 7212 that have their electrodes at the left. Tracks 127 and 128 are located adjacent left main channel member 123, and tracks 126 and 129 adjacent right member 122, the tracks of each pair being spaced apart far enough to prevent interference between the tube brackets 130 which they carry.

Those tube brackets are best shown in FIGS. 9 to 11. They serve to mount the tubes on the tracks in a manner that positively defines the lateral spacing of the tubes from the tracks and also defines the longitudinal tube positions effectively positively but permits their convenient adjustment. The tubes are mounted on brackets 130 by means of the insulating mounting blocks 132 and tongues 134. Each bracket comprises a clamp member 140, which encloses the track on three sides and includes a clamp formation adapted to grip tongue 134; and a foot member 150, by which the clamp member is frictionally secured to the track with the aid of a bridge 152 and a bolt 154.

Insulating mounting block 132 may be formed of a suitable epoxy resin, and is typically cemented directly to the glass surface of the discharge tube by means of epoxy cement. Tongue 134 is preferably of metal, and may be molded into the block 132, as indicated schematically at 135, forming a rigid unit therewith. Tongue 134 is typically provided with locking formations, shown as the two holes 136, to facilitate positive retention and location of the tongue relative to clamp member 140.

Clamp typically comprises a single piece of some what resilient sheet metal, such as stainless steel, of general U-form, with one leg 141 of the U looped back at 142 to form a clamp portion 143 parallel to the leg. Mounting tongue 134 is adapted to be gripped between leg 141 and clamp portion 143, as shown clearly in FIG. 9. The clamp is yieldingly held in closed position by latch fingers 148, which are stamped out from the edge portions of member 140 and are spaced on opposite sides of the tongue (FIG. 10). The free end of portion 143 is typically bent back at 145, forming at the same time a rounded latch surface to engage fingers 148 and a handle whereby the clamp can readily be opened to release tongue 134 by prying action of a screw-driver or similar tool, using the loop 142 as a fulcrum. Two defining bosses 149 are provided on clamp leg 141 in position to enter the holes 136 of tongue 134. Those bosses may be formed by partially punching the sheet material. They preferably extend fittingly into holes 136 far enough to provide reliable definition of the tongue, rendering mounting block 132 and bracket 130 essentially a unitary mounting structure; but permit ready disassembly of the tongue from the clamp assembly upon partial opening of clamp portion 143, as for replacement of a tube.

Clamp member 140 fits snugly about the rectangular channel section of track 126, being normally freely slidable on the track without side play. The clamp is effectively locked in desired position on the track by means of the foot member 150 and bridge 156. Foot member 150 has two foot portions 151 adapted to engage the inner corners of the track channel, and a narrower web portion 152 that is centrally bored to receive the lock screw 154. Bridge 156 is threaded on screw 154. Each end of the bridge carries two spaced ears 158, which enclose the narrowed portion of foot member 150 and extend through side notches 159 in the legs of clamp member 140. When screw 154 is tightened, the foot member is pressed upward, as seen in FIG. 9, relative to clamp member 140, firmly clamping track 126 between the feet 151 and the web portion of the clamp member. At the same time the curved form of ears 158 tends to draw the legs of the clamp member together, insuring firm engagement of the flanges of the track channel. Partial release of screw 154 reduces the frictional clamping action sufiiciently to permit manual sliding of the entire clamp structure along track 126 to adjust the inter-tube spacing. After adjustment, screw 154 may be slightly tightened if necessary to effectively lock the clamp in place.

FIG. 7 illustrates the facility with which the tube spacing may be varied, showing an upper group of tubes with relatively large spacing and a lower group of tubes with relatively small spacing. In actual practice the spacing of both groups would be much smaller than that shown, and would approximate more closely the relation shown in FIGS. 4 and 5, for example. With such spacing the support brackets must either be designed so that their dimension parallel to the track is substantially limited to the tube diameter, or the brackets for adjacent tubes will overlap. The present invention permits such overlapping without interference between adjacent brackets. That is done by providing two tracks at each side of the tube array, and supporting the brackets of adjacent tubes on different tracks. Whereas that feature of the invention obviously does not require that the tracks of each pair be structurally independent, as illustratively shown, it is preferred that the symmetry or orientation of the tracks and brackets be such that a tube may be mounted with its electrode at either side of the array without modification of the bracket structure. In the present embodiment, for example, the two brackets for each tube are mounted with the spring loops 142 pointing toward the electrode end of the tube. Tracks 126 and 127 are adapted to receive the tubes 72a with bracket loops 142 on the right, as seen in FIG. 7; tracks 128 and 129 receive tubes 72b with bracket loops on the left. The spacing between tracks 126 and 127 is preferably the same as that between tracks 128 and 129. A tube can then be reversed on the mounting, if desired, without modification of the bracket structure.

Electrical power for energizing the discharge tubes is provided from a suitable high voltage transformer, not shown, and is distributed to the electrodes of the two groups of oppositely oriented tubes via respective bus bars 170 and 172. Those bus bars are typically mounted on channel members 122 and 123 by means of high voltage insulators, indicated schematically at 174. Connections from the bus bars to the various tubes are indicated at 176, and are sufficiently long and flexible to accommodate the maximum anticipated adjustment movement of the tubes along tracks 126 to 120. Adjustment of the tube spacing may then be carried out conveniently while the tubes are energized. Housing structures may be provided if desired to enclose the bus bars and connections, in a manner similar to that described in connection with FIGS. 1 to 6.

The large improvement in ozone production accomplished by the present invention is believed due to a combination of inter-related features, each of which is useful in and of itself, but which yield optimum results when applied in cooperating relation. One element of that improvement is the use of appreciably increased spacing between adjacent discharge tubes. Prior art devices of the present general type have employed tubing of approximately mm. diameter containing a gas pressure of 6 to 8 mm. of Hg at a spacing of about 0.030 between tubes. Those conditions result in an apparent maximum of activity within the tube, as judged by illumination emitted from the discharge or by current drawn from the power source. The power consumption and brightness both decrease when such tubes are brought almost into contact with each other, and also when the spacing between them is increased much beyond 0.030", say to 0.050. Accordingly, it has been the universal practice to maintain a spacing of approximately 0.030", a value which was not considered to be at all critical.

I have discovered, however, that if the distance between tubes is increased from that value by a factor of two or more, and if adequate voltage is supplied to the tube electrodes, the power consumption and brightness pass through a minimum and reach a second peak. Whereas that peak is not necessarily higher than the broad maximum utilized in previous practice, I have found that the nature of the discharge is altered in a way that leads to increased ozone production. One effect of that increase of tube spacing is beleived to be a transition in the nature of the current flow between adjacent tubes from What may be described as leakage current to an actual breakdown of the intervening air with radically increased accompanying ionization. Such true breakdown is far more effective than the previous leakage current in producing ozone. The most useful tube spacing for producing such breakdown has been found to be a rather critical function of several variables, particularly the available voltage. In contrast to the previous practice of maintaining a rigidly fixed. tube spacing, I provide mounting structure which permits convenient manual adjustment of the tubes while energized, and I then adjust the tube spacing for optimum discharge characteristics during their actual operation. As an illustration and guide, a typical tube spacing for producing the desired type of discharge at an applied voltage of 7,000 to 8,000 is approximately 0.070"; at 9,000 volt approximately 0.080"; and at 10,000 to 12,000 volts the optimum spacing may be 0.125" or more.

A further important feature of the invention concerns the gas pressure within the discharge tube. Increased gas pressure in the discharge would normally be expected to increase the resistance to current flow, and thus reduce the power available to produce ionization and ozone by whatever phenomenon takes place between adjacent tubes. That may be true. But nevertheless, I have found that gas pressures radically higher than those previously employed lead to improved discharge characteristics and increased ozone production.

The visible differences in the nature of the discharge within the tubes have already been described. A practical result of those differences appears to be a far more uniform and dense distribution of the ionization of the air between adjacent tubes. That effect may perhaps be understood in the following Way. With low pressure in the tubes, excitation of the air at a single point appears to draw current from a relatively large volume of gas within the tube, making it impossible for such excitation to occur simultaneously at closely spaced points. The high gas pressure of the present invention, on the other hand, confines the current flow between the tube surface and the central uniform column of the gas discharge to a narrow volume of gas, leaving the neighboring gas available to provide current for excitation of the air between the tubes at closely adjacent points. From that viewpo1nt, the high gas pressure produces a more uniform distribution of the voltage or power available at the inner face of the tubing, whereby more nearly uniform and contmuous discharge excitation can be produced in the air. The modified appearance of the discharge within the tubes appears to be consistent with that view. But in any case, the provision of radically increased gas pressure in the tubes has been found to double or even triple the ozone production that was obtainable per unit length of tubing with prior art devices.

In contrast to the conventional 6 to 8 mm. of Hg, the present invention provides in the discharge tubes a gas pressure of at least approximately 30 mm. of Hg, and preferably about 50 or more. Pressures up to mm. of Hg provide further improvement, and pressures at least as high as about 200 mm. of Hg are highly effective. The upper limit of the practicable pressure is set primarily by the inconvenienece of providing the increased voltage that is required. However, up to 100 or even 200 mm. of Hg that is not a serious problem for many applications. Under extremely disadvantageous conditions, such as have already been described, it is generally preferred to employ pressures of the order of 40 to 80 mm. of Hg, which can be effectively energized with voltages of 8,000 to 10,000, for example. As already emphasized, optimum benefit from use of such high gas pressures is obtainable by careful adjustment of the tube spacing under direct visual control, as is rendered feasible by the tube mounting structures of the present invention.

A further improvement in the uniformity of the discharge longitudinally of the tube, and reduction in the gas volume that appears to be involved in each point breakdown of the surrounding air, is achieved by the use of far smaller tubing than has previously been considered necessary to carry the discharge. In previous ozone generators employing spaced discharge tubes of the described type, it has been considered necessary to employ tubing of approximately 15 mm. diameter or more to distribute the available voltage over a satisfactory length of tube.

I have found, however, that the scale of the visible fine structure of the discharge, by which current is apparently carried between the central uniform column and the tube wall, is roughly proportional to the diameter of the tube. A point discharge between adjacent tubes is thus associated in a large tube with ionization of gas immediately within the tube wall over a relatively large area. By utilizing small tubing in accordance with the present invention the volume of that local ionization is greatly reduced, permitting the adjoining gas to carry current for another point excitation of the air at a closely spaced point between the tubes. Thus, with small tubes, a greater number of inter-tube discharges per unit length of the tubes is made possible, leading to correspondingly increased ozone production. That novel action is similar to, and directly supplements, the above described result of employing high gas pressure. The preferred range of tubing sizes is from about to about 8 mm. diameter. Still smaller sizes can be used effectively, but tend to be inconvenient because of difliculty of maintaining uniform spacing between the tubes over their entire length.

The described advantages to be gained from use of high gas pressures, small tube diameters and large intertube spacing require careful pumping and outgassing of the tubes and electrodes and use of pure gas for filling the tubes. After thorough elimination of oxygen and nitrogen by pumping the tubes at elevated temperature, I fill the tubes with mercury-free noble gas, typically neon or argon, to the desired pressure. The tubes are then sealed off in the usual way.

I claim:

1. An ozone generator comprising in combination a plurality of discharge tubes each having an electrode at one end and containing essentially oxygen-free ionizable noble gas at a pressure that exceeds 30 mm. of mercury,

said tubes having a diameter between about 6 and about 8 mm., means for mounting the tubes in mutually spaced parallel relation in a common plane with the electrodes of adjacent tubes at opposite ends thereof, and means for supplying alternating current at tube energizing voltage to the tube electrodes.

2. An ozone generator as defined in claim 1, and wherein said mounting means for the tubes comprise means actuable to confine the tubes to said common plane while permitting each tube to be individually moved parallel to said plane for varying the mutual spacing between them during said current supply.

3. An ozone generator comprising in combination a plurality of substantially straight discharge tubes each having an electrode at one end,

a rigid support frame,

two pairs of elongated resilient mounting pads having respective longitudinally uniform working surfaces,

means mounting the pads of each pair in mutually opposed relation on the frame with their working surfaces engaging opposite faces of each tube adjacent an end thereof,

compressing means releasably operable to move the mounting pads of each pair forcibly together to adjustably compress the pads against the tubes,

means for positively limiting the mutual approach of the pads of each pair to such spacing that the tubes are individually manually movable longitudinally of the pads and against the friction thereof to adjustably vary the spacing between adjacent tubes,

and means for supplying alternating current at tube energizing voltage to the tube electrodes during said variation of the tube spacing.

4. An ozone generator comprising in combination at least four track formations mounted in mutually parallel spaced relation,

a plurality of bracket structures mounted on each of the track formation for movement longitudinally thereof,

a plurality of discharge tubes each having an electrode at one end,

means supporting each of the tubes transversely of the track formations with one end portion supported on a bracket structure on one track formation and the other end portion supported on a bracket structure on another track formation, the tubes extending in mutually parallel spaced relation with the electrodes of adjacent tubes at opposite ends thereof,

the respective tubes of each pair of adjacent tubes being supported on bracket structures on different track formations, whereby the bracket structures supporting adjacent tubes may overlap longitudinally of the track formations,

releasable means for effectively locking the bracket structures against longitudinal movement on their respective track formations,

the bracket structures being individually movable longitudinally of the track formations on release of said releasable means to adjustably vary the spacing between adjacent tubes,

and means for supplying alternating current at tube energizing voltage to the tube electrodes during said movement of the bracket structures.

5. An ozone generator comprising in combination a plurality of discharge tubes each having an electrode at one end and two elongated support elements fixedly mounted on the tube and extending radially therefrom in a common plane and in mutually spaced parallel relation,

a plurality of track members of channel section mounted in mutually parallel spaced relation with the channel webs in a common plane and the channel flanges extending in a common direction from said plane,

a plurality of bracket structures mounted on each of the track members for movement longitudinally thereof, each said bracket structure comprising a slide member of U-form adapted to slidingly engage the outer faces of the web and flanges of the track member, a leg member of U-form with two foot formations adapted to engage the inner angles of the track member channel, and releasable means for variably urging the slide member and leg member toward each other while spreading the foot formations of the leg member and drawing the legs of the slide member together to effectively lock the slide structure in fixed relation to the track member,

clamp structures carried by the respective bracket structures and each adapted to releasably receive one of the tube support elements for mounting the tubes in mutually parallel relation transversely of the track members and parallel to said common plane of the channel webs,

11 12 the bracket structures being individually movable longisaid tubes having a diameter between about 6 and tudinally of the track members on release of said about 8 mm.

releasable means to adjustably vary the spacing between adjacent tubes, References Cited by the Examiner and means for supplying alternating current at tube 5 UNITED STATES PATENTS energizing voltage to the tube electrodes during said 2 537 53 51 H f 204 320 movement of the bracket structures. 2,710 553 5 6 195 5 Pardey 204 317 6. An ozone generator as defined in claim 5 and Where- 2,745,407 5/1956 M ll t 1 204 32() in said discharge tubes contain essentially oxygen-free ionizable noble gas at a pressure that exceeds 30 mm. of 10 JOHN MACK Prmary Examine"- mercury, WINSTON A. DOUGLAS, Examiner. 

4. AN OZONE GENERATOR COMPRISING IN COMBINATION AT LEAST FOUR TRACK FORMATIONS MOUNTED IN MUTUALLY PARALLEL SPACED RELATION, A PLURALITY OF BRACKET STRUCTURES MOUNTED ON EACH OF THE TRACK FORMATION FOR MOVEMENT LONGITUDINALLY THEREOF, A PLURALITY OF DISCHARGE TUBES EACH HAVING AN ELECTRODE AT ONE END, MEANS SUPPORTING EACH OF THE TUBES TRANSVERSELY OF THE TRACK FORMATIONS WITH ONE END PORTION SUPPORTED ON A BRACKET STRUCTURE ON ONE TRACK FORMATION AND THE OTHER END PORTION SUPPORTED ON A BRACKET STRUCTURE ON ANOTHER TRACK FORMATION, THE TUBES EXTENDING IN MUTUALLY PARALLEL SPACED RELATION WITH THE ELECTRODES OF ADJACENT TUBES AT OPPOSITE ENDS THEREOF, THE RESPECTIVE TUBES OF EACH PAIR OF ADJACENT TUBES BEING SUPPORTED ON BRACKET STRUCTURES ON DIFFERENT TRACK 